Egypt's Islamist president unilaterally decreed greater authorities for himself Thursday and effectively neutralized a judicial system that had emerged as a key opponent by declaring that the courts are barred from challenging his decisions.

CAIRO — Egypt's Islamist president unilaterally decreed greater authorities for himself Thursday and effectively neutralized a judicial system that had emerged as a key opponent by declaring that the courts are barred from challenging his decisions.

Riding high on U.S. and international praise for mediating a Gaza cease-fire, Mohammed Morsi put himself above oversight and gave protection to the Islamist-led assembly writing a new constitution from a looming threat of dissolution by court order.

But the move is likely to fuel growing public anger that he and his Muslim Brotherhood are seizing too much power.

In what was interpreted by rights activists as a de facto declaration of emergency law, one of Morsi's decrees gave him the power to take "due measures and steps" to deal with any "threat" to the revolution, national unity and safety or anything that obstructs the work of state institutions.

Morsi framed his decisions as necessary to protect the revolution that toppled Hosni Mubarak nearly two years ago and to cement the nation's transition to democratic rule. Many activists, including opponents of the Brotherhood, criticize the judiciary as packed with judges and prosecutors sympathetic to Mubarak. Brotherhood supporters accuse the courts of trying to block their agenda.

"He had to act to save the country and protect the course of the revolution," said one of Morsi's aides, Pakinam al-Sharqawi, speaking on Al-Jazeera. "It is a major stage in the process of completing the January 25th revolution," she said, alluding to the starting day of last year's uprising against Mubarak.

In a nod to revolutionary sentiment, Morsi also ordered the retrial of Mubarak and top aides on charges of killing protesters during the uprising. He also created a new "protection of the revolution" judicial body to swiftly carry out the prosecutions. But he did not order retrials for lower-level police acquitted of such killings, another widespread popular demand that would disillusion the security forces if carried out.

Liberal politicians immediately criticized the decrees as dictatorial and destined to divide a nation already reeling from months of turmoil following Mubarak's ouster. Some said they exceeded the powers once enjoyed by Mubarak.

"Morsi today usurped all state powers & appointed himself Egypt's new pharaoh," pro-reform leader Mohamed ElBaradei wrote on Twitter. "A major blow to the revolution that could have dire consequences."

ElBaradei later addressed a news conference flanked by other prominent politicians from outside the Brotherhood, including two presidential candidates who ran against Morsi, Amr Moussa and Hamdeen Sabahi.

They pledged to cooperate to force Morsi to rescind his assumption of greater powers. "We will work together as Egyptians until we achieve the goals of our revolution," said ElBaradei, a former director of the U.N.'s nuclear agency and Nobel peace laureate.

They called for mass protests Friday to demand the dissolution of the declarations. The audience interrupted the press conference, chanting "Down with the Guide's rule," referring to the Supreme Guide of Morsi's Muslim Brotherhood group, Mohammed Badie.

The prospect of large rival protests involving Morsi's opponents and supporters in Cairo on Friday raises the likelihood of clashes.

Thousands from the rival camps were already out on the streets of Cairo late Thursday in an increasingly charged atmosphere.

A crowd of Brotherhood supporters massed outside the Supreme Court building and offices of the prosecutor general — whom Morsi removed in Thursday's edict. They chanted slogans for "the cleansing of the judiciary," shouting, "The people support the president's decisions." Leading Brotherhood member Mohammed el-Beltagi, attending the rally, singled out several critics of Morsi from among the ranks of the judiciary for criticism.